1. Field of the Invention
This invention relates to air compressors, and relates more particularly to-an improved structure of air compressor which uses two air inlets and one air outlet to achieve high compression ratio.
2. Description of the Prior Art
FIG. 5 shows an air compressor according to the prior art. The air compressor comprises a motor 5, a mounting plate 5, a transmission gear 7, a cylinder 8, and a coupling block 9. The motor 5 is fastened to the mounting plate 6 by screws, having a pinion 50 on the output shaft thereof meshed with the transmission gear 7. The mounting plate 6 has a shaft 60 mounted on the vertical wall thereof. The transmission gear 7 is fixedly mounted around the shaft 60 at one end. A counterweight 61 is fastened to the shaft 60 at an opposite end. The counterweight 61 has a coupling rod 62 at one side coupled to a link 63. The cylinder 8 is mounted on the horizontal wall of the mounting plate 6 to hold a piston 80. The piston 80 is connected. to the link 63. The coupling block 9 is fastened to the top side of the cylinder 8 by screws 81, having an air input chamber 91 and an air inlet 90 for guiding outside air into the air input chamber 91. The air inlet 90 is controlled by a valve block 92, which is supported on a spring 93. The coupling block 9 further comprises an output chamber 94 and a guide tube 95 connected to the output chamber 94. The output chamber 94 is controlled by a valve block 96, which is supported on a spring 97. When the piston 80 is moved downwards by the link 63, outside air is drawn into the cylinder 8. When the piston 80 is moved upwards, the air inlet 90 is closed, and compressed air is driven out of the cylinder 8 through the guide tube 95. This structure of air compressor is functional, however its compression ration is low. Because of low compression ratio, the motor wears quickly with use.